Sheet-metal elements made of flexibly rolled material strip

ABSTRACT

The invention relates to sheet-metal elements made of flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip. A solution according to the invention consists in a sheet-metal element reshaped about the longitudinal direction of the strip or reshaped transverse to the longitudinal direction of the strip from a flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip to form a tube or profile body having an out-of-round cross-section and variable wall thickness over the length or over the circumference.

The invention relates to sheet-metal elements made of flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip.

BACKGROUND OF THE INVENTION

Flexibly rolled material strip is produced by rolling starting material having an initially constant thickness with variable roller gap thickness. Such rolling methods to produce flexibly rolled material strip and reshaping methods to produce sheet-metal elements therefrom are known from the prior art.

DE-PS 104 875 describes how a strip-shaped or flat piece of sheet-metal is brought to different wall thicknesses by rolling out, and from the piece of sheet-metal having variable wall thicknesses thus obtained, a tube having different wall thickness in the longitudinal direction is bent round and soldered along the slit.

From EP 0 788 849 A1 it is known to first roll a metal sheet such that parallel indentations are formed transverse to the direction of rolling, wherein the rolled sheet-metal is then cut to size and the pieces of sheet-metal are finished to form tubes having variable wall thickness in the longitudinal direction by reshaping the rolled metal sheet and joining the butting edges.

Sheet-metal elements having uniform cross-section or variable cross-section in one longitudinal direction can be exposed to different loadings in different longitudinal and circumferential sections when used as intended. When manufacturing sheet-metal elements from material having uniform wall thickness, the areas exposed to lower loading are thus over-dimensioned and result in excessive weight of the component. This is especially undesirable in vehicle construction.

It is furthermore known that in vehicle construction a defined deformation behavior is required of sheet-metal elements when exceeding their strength limit, that is in the case of a vehicle crash. Such deformation behavior can be brought about by shaping the sheet-metal elements and/or by using sheet-metal elements having wall thickness varying over the length or over the circumference.

OBJECT OF THE INVENTION

The object of the present invention is to provide sheet-metal elements made of flexibly rolled material strip which allow extended usage of such sheet-metal elements in vehicle construction, especially as chassis and vehicle components and as bodywork parts.

SUMMARY AND DETAIL DESCRIPTION OF THE INVENTION

Insofar as flexibly rolled material strip is discussed here, this includes both the possibility of reshaping the material strip, which has not been divided, after rolling to form sheet-metal elements and then cutting to length. Also the material strip may be cut to length after the flexible rolling and then reshaped to form sheet-metal elements. And finally, the material strip may be cut to length before the flexible rolling, and then reshaping flexibly rolled blanks to form sheet-metal elements.

The sheet-metal elements described hereinafter preferably comprise sheet-metal elements manufactured of cold-rolled material strip.

A first solution according to the invention consists in a sheet-metal element reshaped about the longitudinal direction of the strip from a flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip to form a tube or profile body having an out-of-round cross-section and variable wall thickness over the length.

A second solution consists in a sheet-metal element reshaped transverse to the longitudinal direction of the strip from flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip to form a tube or profile body having an out-of-round cross-section and variable wall thickness over the circumference.

The out-of-round profile cross-section can mean uniform or symmetrical cross-sections, for example, polygonal or oval cross-sections, or also completely asymmetric cross-sections. The alternatives of a longitudinally welded closed profile or a profile which is open in cross-section are included here. The sheet-metal elements according to the first solution especially under axial loading show regionally different deformation behavior while the sheet-metal elements according to the second solution can especially exhibit different behavior under bending in different planes. Both can be specifically used for the purposes of saving weight and pre-defined deformation in longitudinal vehicle supporting members or in lateral supporting members (side impact protection).

In a particular embodiment, it is provided that the sheet-metal elements have a variable cross-section in the longitudinal direction, especially a continuously and similarly varying cross-section. This can be brought about by cutting the material strip to length where one or two wedge-shaped elements are cut away or by joining the material strip such that it overlaps, with increasing overlapping.

According to a further embodiment, it is provided that the sheet-metal elements have longitudinal sections which differ from the uniform, for example, a round cross-section. This can be accomplished by subsequently reshaping originally uniformly shaped profiles, for example, using an internal high-pressure deformation process in which individual profile sections are radially expanded or using a conventional reshaping method such as rolling or pressing in which individual profile sections are reduced in cross-section or deformed.

Furthermore, the sheet-metal elements can run curved in the longitudinal direction wherein preferably straight profiles are first manufactured which are then bent.

The sheet-metal elements can have a constant inner cross-section with differences in wall thickness on the outside or a constant outer cross-section with differences in wall thickness on the inside. Both can be achieved by suitable flexible rolling of the starting material and suitable deformation steps. If the material strip is produced with symmetrical variations in thickness at one longitudinal plane, the differences in wall thickness on the finished component are made noticeable on the inside and on the outside.

For the aforementioned purposes of saving weight and defined deformation behavior, especially large and especially flowing differences in thickness can be particularly advantageous. For this purpose it is proposed that the difference in wall thickness relative to the maximum thickness should be at least 25% on the flexibly rolled starting material and thus on the sheet-metal element.

In order to further increase the saving in weight and the differentiated deformation behavior, it can be advantageous if the sheet-metal elements are provided with punched holes in their wall surface, these preferably being produced on the flexible material strip before the reshaping to form the sheet-metal element. On the other hand, in order to increase the strength, it can be advantageous if the wall surfaces are provided with structures, for instance, indentations in a uniform grid arrangement, and this can also favorably influence the self-oscillation behavior of the sheet-metal elements.

Further advantageous embodiments consist in the fact that the sheet-metal elements may have an end section with greater wall thickness which allows favorable axial connection and/or that at least one of the end sections is expanded in cross-section as a push-fit fitting in order to make plug connections between components of the same kind.

Another solution comprises a sheet-metal element with variable wall thickness in one direction, which is reshaped in a direction substantially parallel to the longitudinal direction of the strip from a flexibly rolled material strip having different thicknesses in the longitudinal direction. The strip forms a curved or corrugated surface element so that regions of equal wall thickness run perpendicular to the direction of beads, edges or cylinder lines.

Another solution comprises a sheet-metal element with variable wall thickness in one direction, which is reshaped substantially perpendicular to the longitudinal direction of the strip from a flexibly rolled material strip having different thicknesses in the longitudinal direction. The strip forms a curved or corrugated surface element so that regions of equal wall thickness run parallel to the direction of beads, edges or cylinder lines.

A last solution comprises a sheet-metal element with variable wall thickness in one direction, which is reshaped from flexibly rolled material strip having different thicknesses in the longitudinal direction. The strip forms a spatially deformed surface element, for example, in this case, lines of intersection deviating from a straight line are formed in the direction of two perpendicularly intersecting sections. This also includes matching lines of intersection in rotationally symmetrical sheet-metal elements.

In the sheet-metal elements hereby defined the regions of greater wall thickness running parallel to one another can also serve to increase the strength with a simultaneous saving in weight as a result of the interposed regions of smaller wall thickness. The regions of smaller wall thickness can also be used as predefined deformation regions in the event of the strength limit being exceeded. In the aforesaid spatially deformed sheet-metal elements the self-osciallaiton behavior can especially be influenced with a simultaneous saving of material.

In a preferred embodiment, a plurality of the sheet-metal elements can be brought together along longitudinal edges to form a surface element or a plurality of the sheet-metal elements can be brought together along a plurality of parallel longitudinal edges to form a hollow body. In this case, open-ended hollow bodies are formed. Finally, a plurality of said sheet-metal elements can be brought together along circumferential edges to form a hollow body.

Hollow bodies closed on three or four sides may be produced. The hollow bodies can also have a variable cross-section in one longitudinal direction, especially a continuously and similarly varying cross-section. The sheet-metal elements can also have longitudinal sections which differ from a uniform cross-section in one longitudinal direction. Finally, they can also run curved in one longitudinal direction. In the case of the sheet-metal elements in the form of hollow bodies, constant inner cross-sections with differences in wall thickness on the outside and constant outer cross-sections with differences in wall thickness on the inside can also be realized.

For the aforesaid reasons, a difference in wall thickness of at least 25% relative to the maximum thickness is also to be preferred here. To save weight, the wall surfaces can again be provided with punched holes or to increase strength, they can have a wall structure, such as indentations in a uniform grid. The sheet-metal elements hereby described can also have sections of greater wall thickness to improve the connection, especially by welded joints. In the case of oblong sheet-metal elements of the type having closed cross-sections, in this case also, one of the end sections can be expanded in cross-seciton as a push-fit fitting.

Sheet-metal elements according to the invention as profile bodies having variable wall thickness in the longitudinal direction can especially be used as vehicle supporting members having defined graded loading or deformation behavior in the longitudinal direction in motor vehicles. In this case, a bending strength which differs over length is also appropriate when different bending loads act on the supporting members, such as a compressive or buckling strength which differs over the length for supporting members exposed to axial forces in the case of a crash. In addition, sheet-metal elements with said properties can also be used as impact absorbers having defined graded deformation behavior in the longitudinal direction. A design based on controlled axial shortening in the case of a crash is hereby made possible.

According to another proposal, sheet-metal elements according to the invention as profile bodies having variable wall thickness in the circumferential direction can also be used as vehicle supporting members having defined graded deformation behavior or buckling behavior over the circumference. In this case, a higher geometrical moment of inertia is to be provided in the main bending plane of the supporting member while a lower geometrical moment of inertia can be provided in the bending planes exposed to lower loading in order to save material.

Without being restrictive, the following applications of profiles according to the invention in vehicles may be mentioned: longitudinal supporting members (front, back), shock absorbers (front, back), axle cross members, seat cross members, sills, tunnel reinforcement profiles, A, B and C pillars, roof frames and roof cross members.

Flat sheet-metal elements according to the invention can also be used as bodywork outer panels, where cross-pieces having greater wall strength can also take on the function of beads or grooves with regard to increased form stability. In this case, even a specific reinforcement of the structure can be brought about for the case of a side-on crash.

Another preferred use of flat sheet-metal elements comprises a vehicle floor pan including the tunnel which can be composed of various sheet-metal elements which can be optimized with respect to their strength and their weight by using flexibly rolled material. The structural strength for various cases of crashes can also hereby be improved with reduced usage of material.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are shown in the drawings and are described hereinafter.

FIG. 1 shows an open rectangular profile with variable wall thickness over the length;

FIG. 2 shows an open half-round profile with variable wall thickness over the length;

FIG. 3 shows a closed rectangular profile with variable wall thickness in circumferential direction;

FIG. 4 shows a closed oval profile with variable wall thickness in circumferential direction;

FIG. 5 shows a closed oval profile with variable wall thickness over the length;

FIG. 6 shows an oval profile with variable wall thickness over the length and lateral flat portions;

FIG. 7 shows a closed rectangular profile with variable wall thickness over the length;

FIG. 8 shows an U-profile with variable wall thickness over the length, being finally bended;

FIG. 9 shows a sheet-metal element with variable wall thickness, which is deformed parallel to the longitudinal direction;

FIG. 10 shows a sheet-metal element with variable wall thickness, which is deformed perpendicular to the longitudinal direction;

FIG. 11 shows a sheet-metal element, which is deformed parallel to the longitudinal direction;

FIG. 12 shows one example for the application of a sheet-metal element according to FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT IN THE DRAWINGS

In FIG. 1 there is an open U-form respectively rectangular profile 11, which in longitudinal direction has a variable wall thickness. Herein a first longitudinal portion 12 with a smaller constant wall thickness, a transition portion 13 with increasing wall thickness and a second longitudinal portion 14 with constant greater wall thickness are to be seen. The profile has a constant free inner cross section in the longitudinal direction.

In FIG. 2 there is shown an open profile 15 with half-round cross section, which has variable wall thickness in the longitudinal direction. Herein a first longitudinal portion 16 with smaller constant wall thickness, a transition portion 17, and a second longitudinal portion 18 with greater constant wall thickness are to be seen. The profile has a free inner cross section changing in the longitudinal direction.

In FIG. 3 there is shown a closed, mostly rectangular profile 21, which has a substantially constant cross section in the longitudinal direction and in the cross section a longer sidewall 22 with a minimal wall thickness, two sidewalls 23 and 24 with a greater wall thickness and a sidewall 25 with a maximal wall thickness.

In FIG. 4 there is shown a closed oval profile 26, having a constant cross section over the length, wherein the wall thickness changes from a circumferential portion 27 with a smallest wall thickness to a circumferential portion 28 with a maximal wall thickness.

In FIG. 5 there is shown a closed oval profile or tube 31, which has a constant wall thickness in circumferential direction and a decreasing wall thickness from a greater end opening 32 to a smaller end opening 33. Herein the free cross section of the tube is reduced as well.

In FIG. 6 there is shown an oval profile 35 with basically constant cross section and changing wall thickness over the length (not shown). In addition this profile has a lateral flattening 36 at one end and furthermore in a middle longitudinal portion a lateral flattening 37.

In FIG. 7 there is shown a multi-edge profile or tube 41, which is connected to an end wall 42. The tube has a constant cross section and in a circumferential direction a constant wall thickness. The tube comprises a first longitudinal portion 43 with a greater wall thickness, a portion of transition 44 with decreasing wall thickness, a second longitudinal portion 45 with reduced wall thickness and a final portion 46 with decreasing wall thickness. This structure is only for example. Different variations of wall thickness are possible.

In FIG. 8 there is shown an open U-profile, which in addition has a bended offset. There are three longitudinal portions 52, 53 and 54 with increasing wall thickness. Starting from portion 54 there are three further portions 55, 56 and 57 with each decreasing wall thickness. Portions of transmission are not identified. Nevertheless the changes in wall thickness may be assumed as steady or smooth.

In FIG. 9 there is shown a metal sheet element 61, having a longitudinal portion 62 of greater wall thickness, a transition portion 63 and a longitudinal portion 64 of smaller wall thickness. Parallel to the longitudinal direction or rolling direction there are indentations 65 and 66 in the sheet material.

In FIG. 10 there is shown a sheet-metal element 71 having in a longitudinal direction or rolling direction a portion 72 with smaller wall thickness, a portion 73 of greater wall thickness and a portion 74 of smaller wall thickness. Portions of transition are not identified in detail. Rectangular with respect to the longitudinal direction, the sheet-metal element has indentations 75 and 76.

In FIG. 11 there is shown a sheet-metal element 81, having in a longitudinal direction or rolling direction a first portion 82 of greater wall thickness, a transition portion 83 and a further longitudinal portion 84 of small wall thickness. There is a profiling 85 parallel to the longitudinal direction as well as a multiplicity of pressed longitudinally running beads 86.

In FIG. 12 there is shown the application of a sheet-metal element according to FIG. 11 as an example. A metal sheet for a vehicle door 91 comprises a first longitudinal portion 92 with smaller wall thickness, a portion of transition 93 and a further longitudinal portion 94 with greater wall thickness. 

1. A sheet-metal element reshaped about the longitudinal direction of the strip from flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip to form a tube or profile body having an out-of-round cross-section and variable wall thickness over the length.
 2. A sheet-metal element reshaped transverse to the longitudinal direction of the strip from flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip to form a tube or profile body having an out-of-round cross-section and variable wall thickness over the circumference.
 3. The element according to claims 1 or 2, wherein it is closed in cross-section and welded in the longitudinal direction.
 4. The element according to claims 1 or 2, wherein it is open in cross-section.
 5. The element according to claim 1, wherein it has a variable cross-section in the longitudinal direction, especially a continuously and similarly varying cross-section.
 6. The element according to claim 2, wherein it has longitudinal sections which differ from the uniform cross-section.
 7. The element according to claim 5, wherein it runs curved in the longitudinal direction.
 8. The element according to claim 6, wherein it has a constant inner cross-section and differences in wall thickness on the outside.
 9. The element according to claim 5, wherein it has a constant outer cross-section and differences in wall thickness on the inside.
 10. The element according to claim 6, wherein the difference in wall thickness is at least 25% relative to the maximum thickness.
 11. The element according to claim 10, wherein it is provided with indentations, especially in a uniform grid arrangement.
 12. The element according to any claims 9, wherein it is provided with punched holes in its surface.
 13. The element according to claim 12, wherein it has end sections having greater wall thickness.
 14. The element according to claim 13, wherein at least one of the end sections is broadened in cross-section as a push-fit fitting.
 15. Sheet-metal element with variable wall thickness in one direction, which is reshaped in a direction substantially parallel to the longitudinal direction of the strip from flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip to form a corrugated surface element so that regions of equal wall thickness run perpendicular to the direction of beads, edges or cylinder lines.
 16. Sheet-metal element with variable wall thickness in one direction, which is reshaped substantially perpendicular to the longitudinal direction of the strip from flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip to form a corrugated surface element so that regions of equal wall thickness run parallel to the direction of beads, edges or cylinder lines.
 17. Sheet-metal element with variable wall thickness in one direction, which is reshaped from flexibly rolled material strip having different thicknesses in the longitudinal direction of the strip to form a spatially deformed surface element.
 18. Sheet-metal element composed of a plurality of sheet-metal elements according to claims 15 or 17 along longitudinal edges to form a surface element.
 19. Sheet-metal element composed of a plurality of sheet-metal elements according to claims 15 or 17 along longitudinal edges to form a hollow body.
 20. Sheet-metal element composed of a plurality of sheet-metal elements according to claims 15 or 17 along circumferential edges to form a hollow body.
 21. Sheet-metal element composed of a plurality of sheet-metal elements according to claim 16 along longitudinal edges to form a surface element.
 22. Sheet-metal element composed of a plurality of sheet-metal elements according to claim 16 along longitudinal edges to form a hollow body.
 23. Sheet-metal element composed of a plurality of sheet-metal elements according to claim 16 along circumferential edges to form a hollow body.
 24. The element according to claim 19, characterized in that it is open at two ends.
 25. The element according to claim 22 or 23, wherein it has a variable cross-section in one longitudinal direction, especially a continuously and similarly varying cross-section.
 26. The element according to claims 22 or 23, wherein it has longitudinal sections which differ from a uniform cross-section in one longitudinal direction.
 27. The element according to claim 26, wherein it runs curved in the longitudinal direction.
 28. The element according to claim 27, wherein it has a constant inner cross-section and differences in wall thickness on the outside.
 29. The element according to claim 27, wherein it has a constant outer cross-section and differences in wall thickness on the inside.
 30. The element according to claim 29, wherein the difference in wall thickness is at least 25% relative to the maximum thickness.
 31. The element according to claim 30, wherein it is provided with indentations, especially in a uniform grid arrangement.
 32. The element according to claim 31, wherein it is provided with punched holes in its surface.
 33. The element according to claim 20, wherein it has end sections having greater wall thickness.
 34. The element according to claim 33, wherein at least one of the end sections is broadened in cross-section as a push-fit fitting.
 35. Use of sheet-metal element according to claims 1 or 3 as a vehicle supporting member having a defined graded loading or deformation behavior in the longitudinal direction.
 36. Use of a sheet-metal element according to claims 1 or 3 as impact absorber having a defined graded loading or deformation behavior in the longitudinal direction.
 37. Use of a sheet-metal element according to claims 2 or 16 as a vehicle supporting member having a defined graded deformation behavior over the circumference.
 38. Use of a sheet-metal element according to claims 15, 16, 17, 21, 22 or 23 as a vehicle floor pan.
 39. Use of a sheet-metal element according to any one of claims 15, 16, 17, 21, 22 or 23 as a vehicle outer panel. 